Control system for automatically starting a continuous casting apparatus



NEH 4045M .J

N 1966 L. E. JENDRASZKIEWICZ E AL 3,283,370

CONTROL SYSTEM FOR AUTOMATICALLY STARTING A CONTINUOUS CASTING APPARATUSFiled April 15, 1964 Aflmj AIOA K PMs/4 )FoLLS g? MOLD UGO/4mm? 2 4 lama5994) ACTH/97706 INVENTORS L50 ids/vpenszk/ew/cz BY Foamy-d K55:

United States Patent Ofilice 3,283,370 CONTROL SYSTEM FOR AUTOMATICALLYSTARTING A CONTINUOUS CASTING AP- PARATUS Leo E. Jendraszkiewicz,Chicago, and Robert J. Keene, Chicago Heights, Ill., assignors to UnitedStates Steel Corporation, a corporation of Delaware Filed Apr. 15, 1964,Ser. No. 359,856 8 Claims. (Cl. 2257.2)

This invention relates in general to the continuous casting of metal andmore particularly to an electrical control system for automaticallystarting the continuous casting apparatus.

The control system of this invention includes means for coordinating andtiming the starting of the sprays, mold oscillator, oil pump and pinchrolls as a function of liquid level in the mold together with a means tocom pensate for fast teeming. It is necessary to instrument anyautomatic system in such a fashion that the design of the mold is notmodified and so that the automatic starting system may be readilyincorporated into presently existing equipment. Thus it is importantthat a simple, uncumbersome system be provided.

In the continuous casting of metal, a flow-through water-cooled mold isprovided to receive molten metal that is teemed from a ladle suspendedabove the mold. The mold cools the metal to form and partially solidifythe casting. Spray units directly spray water on the partiallysolidified casting as it descends from the mold to further solidify it.When starting a mold run, the spray units are started prior to the startof the withdrawal of the casting from the mold so as to be able to checkfor spray failures and to note and correct the total water flow.However, it is important that the sprays not be started until afterthere has been some metal buildup within the mold so that water does notpenetrate into the mold to cause a violet eruption. About a 9 inch metallevel buildup in the mold is sufiicient to keep water from getting intothe mold itself.

During operation of the mold it is customary to oscillate the moldlongitudinally in order to prevent partially solidified metal fromhanging within the mold during withdrawal. In order to avoid fracture ofthe casting skin, it is desirable to attain full mold oscillationfrequency and amplitude by the time the casting starts to be withdrawnfrom the mold. Since the start-up time of the pinch rolls is muchshorter than the start-up time of the mold oscillating apparatus, it isnecessary to start mold oscillation prior to starting the pinch rolls.The pinch rolls are started when the liquid level in the mold hasreached a pre-determined operating level near the top of the mold. Thus,the oscillator must be started prior to the time when the liquid hasreached this operating level. It has been found satisfactory to startthe oscillator when the liquid level has reached the mold mid point. Thetime it takes for the liquid level to build up from the mid point to theoperating point is sufficient to assure that the mold oscillator hasachieved its full operation prior to the initation of the withdrawal ofthe casting by activation of the pinch rolls.

Accordingly, it is a major object of this invention to provide a controlsystem for automatically initiating operation of the casting equipmentin the preferred time sequence.

It is a further object of this invention not only to provide the propersequence between steps that initiate operation of the casting equipmentbut also to assure that there is an appropriate time delay betweensteps.

In starting up the continuous casting equipment, it is important thatthe residence time of the liquid that is initially poured into the moldbe long enough so that a 3 ,283 ,3 70 Patented Nov. 8, 1966 skin isdeveloped which is sufficiently thick and strong as to avoid moltenmetal break-out when the casting is withdrawn.

Thus it is a further object of this invention to provide an automaticstart-up system that includes a means for delaying the start of thepinch rolls until a predetermined time period after teeming of theliquid from the ladle into the mold starts.

In brief, the control system of this invention involves a series oftemperature-responsive relays which are spaced at appropriate intervalsalong the wall of the continuous casting mold so as to initiate variousoperations connected with the continuous casting process in the rightsequence, the right time intervals and with regard to the liquid levelin the mold. A temperature-responsive relay nine inches above the bottomof the mold initiates the operation of the upper and lower sprays. Atemperatureresponsive relay mid-way along the length of the moldinitiates operation of the oil pump and of the mold oscillator. Atemperature-responsive relay near the top of the mold normally initiatesoperation of the pinch rolls. In addition, a time delay relay which isenergized by the closing of the relays at the bottom of the mold is inthe circuit to the pinch rolls so as to assure that a minimum time willelapse between the start of teeming and the operation of the pinch rollsthereby providing insurance that the casting skin will have become thickenough to prevent metal breakout once the casting starts to bewithdrawn.

Other objects and purposes of this invention will become obvious from aconsideration of the following detailed description and the drawing, inwhich:

The figure is an electrical and mechanical schematic of an embodiment ofthe control system of this invention.

With reference to the figure, the electrical control system is shown inassociation with a continuous-casting mold 10 having a side wall 11 anda through cavity 12 into which the liquid metal is teemed. The liquidmetal contained within the mold cavity 12 is shown at three increasinglevels designated as A, B, and C.

Positioned within the mold wall 11 and near the bottom thereof is a pairof normally open temperatureresponsive relays designated as 20A and 20B.Since these relays 20 are to control the spray units, and since it isdesirable to make sure that the liquid in the mold 10 has reached acertain level before the sprays are turned on in order to avoid thepossibility of having water enter the mold cavity 12 and cause damage,these relays 20 must be located a short distance above the bottom of themold. Nine inches from the bottom of the mold has been found to be asuitable distance. Accordingly, the liquid level A, which represents thepoint where the relays 14 are closed, is about nine inches above thebottom of the mold.

An additional pair of identical relays 30A and 30B are located andsimilarly positioned at the level B, which is near the mold mid point.In addition, a pair of relays 40A and 40B are located at level C nearthe top of the mold.

Each of the temperature-responsive relays 20, 30 and 40 is separatelyconnected to the line source 14 by the conductor 15 through a manuallyoperated on-oif switch 16. There are two temperature-responsive relaysat each position A, B and C solely in order to provide safety throughredundancy. Thus, as long as one of the two temperature-responsiverelays at each position functions properly, the appropriate operationwill commence at the right time. The redundant temperature-responsiverelays at each position are shown schematically as above one another.Actually they are at the same level.

With regard to the lowermost relays 20, each of these twotemperature-responsive relays 20A and 20B is separately and individuallyconnected to the coils of both of the normally open electromagneticrelays 21 and 22. Relay 21 contacts 21A, when closed, connect theactuating mechanism 23 for the upper cooling sprays to the line 14 whilerelay 22 contacts 22A, when closed, connect the actuating mechanism 24for the lower cooling sprays to the line source 14. During teeming, whenthe liquidmetal level in the mold reaches level A, the mold wall 11adjacent the temperature-responsive relays 20A and 20B reaches atemperature suflicient to operate these relays and thus closes thecircuit from the line 14 to the coils of the relays 21 and 22. The coilsare then energized and the relay contacts 21A and 22A closed to supplypower to the actuating mechanisms 23 and 24 for the upper and lowersprays. Consequently, the sprays begin to operate.

The conductors 25 and 26 operate as a holding mechanism for the relays21 and 22, respectively, so that once these relays 21, 22 are energizedand close, power is supplied to the coils of each relay 21, 22 throughthe conductors 25, 26, respectively. This insures that the relays 21 and22 remain energized and their contacts 21A and 22A remain closed afterinitial energization by the operation of the temperature-responsiverelays 20. Thus, the continued operation of the upper sprays and lowersprays is not dependent upon the continued proper operation of thetemperature-responsive relays 20. Accordingly, any later change oftemperature at the bottom of the mold during its normal operation whichmight cause the relays to open will not effect the operation of thesprays. Similarly, any temporary variation in the liquid level at theposition A during the starting of this continuous casting mold will notcause chatter in the operation of the sprays.

The lamps 27 are lit upon the closing of the temperature-responsiverelays 20 to provide a visible signal indicating the actuation of theserelays. In addition, the lamps 28 are lit upon proper closing of therelay contacts 21A and 22A to provide a visible indication of theoperation of the upper and lower sprays. The manually operated on-oifswitches 29 provide a means for bypass ing the temperature-responsiverelays 20 to permit op erator actuation of the sprays. It should benoted that the switches 29 can be normally open push buttons which maybe released as soon as the sprays are actuated since the holdingmechanism described above will maintain energization of the sprays afterthe switches 29 are reopened. It is to be understood that the lamps 27and 28, as well as the bypassing switches 29 and the main power switch16, are located on a central control panel.

.The temperature-responsive relays 30A, 30B and the associated controlcircuits (including the normally open electromagnetic relays 31 and 32)operate in exactly the same fashion as do the relays 20 and associatedcontrol circuit. Thus a detailed description of their operation will notbe necessary. The temperature-responsive relays 30 are locatedapproximately mid-way along the length of the mold 10. This location isselected with an eye to the location of the temperature-responsiverelays 40, which latter relays 40 control the start of the pinch rolls43. It is desirable that the temperature-responsive relays 30 close toinitiate operation of the mold oscillator 34 sufficiently prior to theclosing of the relays 40 so as to make sure that the mold oscillator 34has achieved full oscillation frequency prior to the time the pinchrolls 43 start to withdraw the casting from the mold 10. This timelagbetween the initial actuation of the pinch rolls 43 and the initialactuation of the mold oscillator 34 is necessary because the start-uptime of the pinch rolls 43 is considerably shorter than the start-uptime for the mold-oscillating apparatus and it is necessary that themold be oscillating at its full frequency prior to the time when thepinch rolls start to withdraw the casting in order to avoid fracture ofthe casting skin within the mold.

It is convenient to initiate the operation of the rapeseed oil pump 33at the same time as initiating the operation of the mold oscillator 34and thus the normally open relay 31, which controls the operation of therapeseed oil pump 33, is connected in parallel with the normally openrelay 32 to be energized by the closing of either one of thetemperature-responsive relays 30.

As the molten metal continues to teem into the mold, the liquid level inthe mold will rise to the level C, near the top of the mold, and closethe temperature-responsive relays 40A, 40B to energize the normallyopenrelay 41 and thereby close a circuit which will initiate operation ofthe pinch rolls 43 and thus start the withdrawal of the casting from themold. Again the circuitry associated with the temperature-responsiverelays 40 is the same as that described in connection with thetemperature-responsive relay 20 (including the holding circuit 45 andmanual bypass switch 49) so that further description is not necessary.

However, normally open contacts 42A of a time delay relay 42 areincluded in the line that leads to the pinch rolls 43 so that theclosing of the temperature-responsive relays 40 by itself isinsuflicient to provide power to the pinch rolls 43. The coil of thetime delay relay 42 is connected to the open side of thetemperature-responsive relays 20 so that the relay 42 is energized uponthe closing of the relays 20 when the liquid level in the mold hasreached the position A. The primary function of this time delay relay 42is to make sure that the metal residence time within the mold 10 hasbeen sufficient to insure the formation of a casting skin of a thicknessadequate to prevent metal break-out once withdrawal of the castingstarts.

This relay 42 may be pre-set to remain open for whatever period of timeis necessary to make sure that the pinch rolls 43 are not operatedbefore a sutficiently thick casting skin has been formed. For example,assume it has been determined that at least 30 seconds should elapsefrom the time the liquid level in the mold reaches level A and theoperation of the pinch rolls begins. Under these circumstances, if theteeming rate becomes extremely rapid and the liquid level reaches levelC before the 30 seconds has elapsed, the time delay relay 42 willprevent the operation of the pinch rolls 43 for the desired 30 seconds.It should be noted that the coil of the time delay relay 42 will remainenergized as long as power is being supplied to the sprays because thecoil of the time delay relay 42 is also connected to the'holdingcircuits 25 and 26. Upon completion of the casting operation, the entirecontrol system may be reset by merely opening the switch 16 which servesto de-energize and consequently open the relays 21, 22, 31, 32, 41 and42.

The units being controlled, such as the pinch rolls 43, are indicated asblack boxes. It should be understood that these black boxes may includethe motors and other operative devices which operate the item beingdesignated. Thus in the claims, a reference to the connection betweenthe third control circuit and the pinch rolls, for example, shall beunderstood to refer to the electrical connection to the motor thatpowers the pinch rolls or to an actuating mechanism that in turncontrols power to the pinch roll motor.

Although one specific embodiment of this invention has been describedand illustrated in some detail, it should be obvious that manyvariations would be possible to those skilled in this art. For example,theredundancy of the temperature-responsive relays at each level isdesirable but not essential to the operation of this invention. It isintended, therefore, in the claims to cover all such variations as wouldbe obvious to one skilled in this art.

What is claimed is:

1; In a continuous casting apparatus having a casting mold, pinch rollsto withdraw a casting from said mold and a spray unit for cooling saidcasting; a control system for automatically starting the operation ofsaid casting apparatus comprising:

first control circuit means, including a first temperature-responsiverelay in the Wall of said mold near the bottom of said mold, to controlpower to said spray unit,

second control circuit means, including a second temperature-responsiverelay in said mold wall near the top of said mold, to control power tosaid pinch rolls, and

time delay means actuated by said first control circuit means andcoupled to said second control circuit means to disenable the connectionbetweensaid second control circuit means and said pinch rolls until apre-determined time after the actuation of said spray unit.

2. The control system of claim 1 wherein said time delay means includesa normally open time delay relay having its normally open contactsbetween said second control circuit and said pinch rolls and having itsenergizing coil coupled to said first control circuit whereby said timedelay relay coil is energized when power is first supplied to said sprayunit.

3. In a continuous casting apparatus having a casting mold, pinch rollsto withdraw a casting from said mold, an oil pump for lubricating theinner surface of said mold, a mold oscillator for longitudinallyoscillating said mold, and a spray unit for cooling said casting; acontrol system for automatically starting the operation of said castingapparatus comprising:

first control circuit means, including a first temperature-responsiverelay in the wall of said mold near the bottom of said mold, to controlpower to said spray unit,

second control circuit means, including a second temperature-responsiverelay in the wall of said mold near the mid point along the length ofsaid mold, to control power to said oil pump and to said oscillator,

third control circuit means, including a third temperature-responsiverelay in said mold wall near the top of said mold, to control power tosaid pinch rolls, and

time delay means actuated by said first control circuit means andcoupled to said third control circuit means to disenable the connectionbetween said third control circuit means and said pinch rolls until apredetermined time after the actuation of said spray unit.

4. In a continuous casting apparatus having a casting mold, pinch rollsto withdraw a casting from said mold, an oil pump for lubricating theinner surface of said mold, a mold oscillator for longitudinallyoscillating said mold, and a spray unit for cooling said casting; acontrol system for automatically starting the operation of said castingapparatus comprising:

a first control circuit to control power to said spray unit, said firstcontrol circuit including a temperature-responsive first relay in thewall of said mold near the bottom of said mold, whereby the presence ofmolten metal at a level in said mold adjacent to saidtemperature-responsive first relay will actuate said first relay tosupply power to said spray unit,

a second control circuit to control power to said oil pump and to saidmold oscillator, said second control circuit including atemperature-responsive sec-ond relay in said mold wall near the midpoint along said mold, whereby the presence of molten metal at said midpoint will actuate said temperature-responsive second relay to supplypower to said oil pump and to said oscillator,

a third control circuit to control power to said pinch rolls, said thirdcontrol circuit including a temperature-responsive third relay in saidmold wall near the top of said mold, whereby the presence of molten 6metal at a level in said mold adjacent to said third relay will actuatesaid third relay to supply power to said pinch rolls, and

time delay means actuated by said first control circuit means andcoupled to said third control circuit to disenable the connectionbetween said third control circuit and said pinch rolls until apre-determined time after power is first supplied to said spray unit.

5. In a continuous casting apparatus having a casting mold, pinch rollsto withdraw a casting from said mold and a spray unit for cooling saidcasting; a control system for automatically starting the operation ofsaid casting apparatus comprising:

first control circuit means to control power to said spray unit, saidfirst control circuit means including a first temperature-responsiverelay in the wall of said mold near the bottom of said mold, whereby thepresence of molten metal at a level in said mold adjacent to said firsttemperature-responsive relay will actuate said relay to supply power tosaid spray unit,

sec-ond control circuit means to control power to said pinch rolls, saidsecond control circuit means including a second temperature-responsiverelay in said mold wall near the top of said mold, whereby the presenceof molten metal in said mold adjacent to said secondtemperature-responsive relay will actuate said second relay to supplypower to said pinch rolls, and

a normally open time delay relay having its normally open contacts inthe line leading from said second control circuit means to said pinchrolls and having its energizing coil coupled to said first controlcircuit means whereby said time delay relay coil is energized when poweris first supplied to said spray unit,

whereby power will be supplied to said pinch rolls only after both theactuation of said second temperature-responsive relay and the closing ofsaid time delay relay contacts.

6. In a continuous casting apparatus having a casting mold, pinch rollsto withdraw a casting from said mold, an oil pump for lubricating theinner surface of said mold, a mold oscillator for longitudinallyoscillating said mold, and a spray unit for cooling said casting; acontrol system for automatically starting the operation of said castingapparatus comprising:

input means adapted to be connected to a source of power,

a temperature-responsive first relay in the wall of said mold near thebottom of said mold, said first relay having normally open contacts inseries with said input means,

an electromagnetic second relay having normally open contacts in seriesbetween said input means and said spray unit and having its energizingcoil in series with said first relay contacts,

a temperature-responsive third relay in said mold wall near the midpoint along said mold and having normally open contacts in series withsaid input means,

an electromagnetic fourth relay having normally open contacts in seriesbetween said input means and said oscillator and having its energizingcoil in series with said third relay contacts,

an electromagnetic fifth relay having normally open contacts in seriesbetween said input means and said pump and having its energizing coil inseries with said third relay contacts,

a temperature-responsive sixth relay in said mold wall near the top ofsaid mold and having normally open contacts in series With said inputmeans,

.an electromagnetic seventh relay having normally open contacts inseries between said input means and said pinch rolls and having itsenergizing coil in series with said sixth relay contacts, and

a time delay relay having normally open contacts in series between saidseventh relay contacts and said pinch rolls, and having its energizingcoil coupled to the input of said spray unit whereby said time delayrelay coil is energized when power is first supplied to said spray unit.

7. In a continuous casting apparatus having a casting mold, pinch rollsto withdraw a casting from said mold, an oil pump for lubricating theinner surface of said mold, a mold oscillator for longitudinallyoscillating said mold, and a spray unit for cooling said casting; acontrol system for automatically starting the operation of said castingapparatus comprising:

input means adapted to be connected to a source of power,

a first control circuit to control power to said spray unit, said firstcontrol circuit including a normally open temperature-responsive firstrelay in the wall of said mold near the bottom of said mold, thenormally open contacts of said first relay being in series with saidinput means, said first control circuit further including a normallyopen electromagnetic sec- 1 nd relay having its normally open contactsin series between said input means and said spray means and having itscoil in series with the normally open contacts of said first relay,whereby the presence of molten metal at a level in said mold adjacent tosaid temperature-responsive first relay will close said first relaycontacts to energize said second relay coil thereby closing said secondrelay contacts to energize said spray unit,

a second control circuit to control power to said oil pump and to saidoscillator, said second control circuit including a normally opentemperature-responsive third relay in the wall of said mold near the midpoint along said mold, the normally open contacts of said third relaybeing in series with said input means, said second control circuitfurther including a normally open electromagnetic fourth relay havingits normally open contacts in series between said input means and saidoil pump and having its coil in series with said normally open contactsof said third relay, said second control circuit further including anormally open electromagnetic fifth relay having its normally opencontacts in series between said input means and said oscillator andhaving its coil in series with said normally open contacts of said thirdrelay, whereby the presence of molten metal at a level in said moldadjacent to said temperature-responsive third relay will close saidthird relay contacts to energize said fourth and fifth relay coilsthereby closing said fourth and fifth relay contacts to energize saidoil pump and said oscillator,

a third control circuit to control power to said pinch rolls, said thirdcontrol circuit including a normally open temperature-responsive sixthrelay in the wall of said mold near the top of said mold, the normallyopen contacts of said sixth relay being in series with said input means,said third control circuit further including a normally openelectromagnetic seventh relay having its normally open contacts inseries between said input means and said pinch rolls and having its coilin series with said normally open contacts of said sixth relay, wherebythe presence of molten metal at a level in said mold adjacent to saidtemperature-responsive sixth relay will close said sixth relay contactsto energize said seventh relay coil thereby closing said seventh relaycontacts to energize said pin-ch rolls, and

a normally open time delay relay having its normally open contacts inseries between said normally open contacts of said electromagneticseventh relay and said pinch rolls and having its energizing coilcoupled to said first control circuit whereby said time delay relay coilis energized when power is first supplied to said spray unit.

8. The control system of claim 7 further characterized by each of saidelectromagnetic relays having a holding circuit whereby the closing ofsaid normally open contacts of each of said electromagnetic relays willsupply power to the energizing coils of each of said electromagneticrelays thereby maintaining power to each of said units controlled byeach of said control circuits regardless of the state of saidtemperature-responsive relays.

References Cited by the Examiner UNITED STATES PATENTS 2,266,249 12/1941 Osterheld. 2,768,413 10/1956 Alexanderson 2257.2 2,772,455 12/ 1956Easter et a1. 2257.2 X 3,204,460 9/1965 Milnes 2257.2 X

J. SPENCER OVERHOLSER, Primary Examiner.

R. S. ANNEAR, Assistant Examiner.

1. IN A CONTINUOUS CASTING APPARATUS HAVING A CASTING MOLD, PINCH ROLLSTO WITHDRAW A CASTING FROM SAID MOLD AND A SPRAY UNIT FOR COOLING SAIDCASTING; A CONTROL SYSTEM FOR AUTOMATICALLY STARTING THE OPERATION OFSAID CASTING APPARATUS COMPRISES: FIRST CONTROL CIRCUIT MEANS, INCLUDINGA FIRST TEMPERATURE-RESPONSIVE RELAY IN THE WALL OF SAID MOLD NEAR THEBOTTOM OF SAID MOLD, TO CONTROL POWER TO SAID SPRAY UNIT, SECOND CONTROLCIRCUIT MEANS, INCLUDING A SECOND TEMPERATURE-RESPONSIVE RELAY IN SAIDMOLD WALL NEAR THE TOP OF SAID MOLD, TO CONTROL POWER TO SAID PINCHROLLS, AND TIME DELAY MEANS ACTUATED BY SAID FIRST CONTROL CIRCUIT MEANSAND COUPLED TO SAID SECOND CONTROL CIRCUIT MEANS TO DISENABLE THECONNECTION BETWEEN SAID SECOND CONTROL CIRCUIT MEANS AND SAID PINNCHROLLS UNTIL A PRE-DETERMINED TIME AFTER THE ACTUATION OF SAID SPRAYUNIT.